Question: $ { {4} \times \left[\begin{array}{rr}{1} & {4} \\ {3} & {-1}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{4}\times{1} & {4}\times{4} \\ {4}\times{3} & {4}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{4} & {16} \\ {12} & {-4}\end{array}\right]}$